build: update license identifiers in setup.cfg (#281)

Author: parthea

packages/google-crc32c/README.md

@@ -24,6 +24,7 @@ Wheels are published for the following platforms / architectures:
 ### Unsupported Platforms
 
 - `manylinux1` platform, `x86_64` architecture support has ended.
+
 See https://github.com/pypa/manylinux/issues/994.
 
 ## Mac OS

packages/google-crc32c/setup.cfg

@@ -23,11 +23,11 @@ author = Google LLC
 author_email = googleapis-packages@google.com
 
 license = Apache 2.0
+license_files = LICENSE
 platforms = Posix, MacOS X, Windows
 classifiers =
     Development Status :: 4 - Beta
     Intended Audience :: Developers
-    License :: OSI Approved :: Apache Software License
     Operating System :: OS Independent
     Programming Language :: Python :: 3
     Programming Language :: Python :: 3.9